Many theories and hypotheses have attempted to explain how SHC might occur, but those which rely on current scientific understanding say that instances mistaken for spontaneous combustion actually required a source of ignition. One such hypothesis is the "wick effect", in which the clothing of the victim soaks up melted human fat and acts like the wick of a candle. Another possibility is that the clothing is caused to burn by a discharge of static electricity. The likelihood that truly spontaneous human combustion actually takes place is remote, due to significant water content and the lack of readily flammable compounds and oxygen in the human body.
The title is derived from one deductive conclusion that he has reached from examining many cases, namely that SHC victims are lonely people who fall into a trance immediately before their incineration.
Heymer suggests that a psychosomatic process in such emotionally-distressed people can trigger off a chain reaction by freeing hydrogen and oxygen within the body and setting off a chain reaction of mitochondrial explosions.
However, Heymer's theories have no basis in scientific theory. Ian Simmons, in a review of The Entrancing Flame, criticized Heymer thus: "He seems to be under the illusion that hydrogen and oxygen exist as gases in the mitochondrial cell [sic] and are thus vulnerable to ignition, which is, in fact, not the case.
The accounts are in the form of written and signed statements from named individuals, shorn of some details to protect the privacy of correspondents. Summaries follow.
It was me. I was lighting up the driveway every couple of steps.
As we got into the garden I thought it was funny at that point. I was walking around in circles saying: 'look at this, mum, look!' She started screaming and my brother came to the door and started screaming and shouting 'Have you never heard of spontaneous human combustion?'
I screamed at her to get her shoes off and it [the flashes] kept going so I hassled her through and got her into the bath. I thought that the bath is wired to earth. It was a blue light you know what they call electric blue. She thought it was fun, she was laughing.
I was stood in the kitchen and my daughter just screamed out that my back was on fire. As I looked down it sort of whooshed all over me. It was like yellow and blue flames all over me. I was not burned at all. Not even my hair was burned.
I was not wearing any nylon clothing [at the time of the flashes]. I used to suffer a lot with static electricity so I tended not to wear anything nylon. I used to crackle with static when taking off my clothes and if I touched any metal thing it used to hurt me. I used to have a lot of trouble with electrical things. They would break down or blow up.
I had just washed and dried my hair [at the time of the incident]. I used to have a lot of static electricity when I was younger. I used to get shocks from touching fridges, things like that.
In the first chapter of the novel Jacob Faithful (1834) by Frederick Marryat there is a vivid account of the hero's mother perishing "in that very peculiar and dreadful manner, which does sometimes, although rarely, occur, to those who indulge in an immoderate use of spirituous liquor. Cases of this kind do, indeed, present themselves but once in a century, but the occurrence of them is too well authenticated. She perished from what is termed spontaneous combustion, an inflammation of the gases generated from the spirits absorbed into the system."
Examples of spontaneous combustion occur in three works by the nineteenth-century Russian author Nikolai Gogol. In the story "St. John's Eve" from Gogol's "Village Evenings Near Dikanka" (1831-32) the guilty character Petro the orphan spontaneously combusts when confronted with a vision of a child he had killed. In the story "Vii," a huntsman in a Cossack village combusts after an encounter with a witch: "And once, when they came to the stable, instead of him there was just a heap of ashes and an empty bucket lying there: he burned up, burned up of his own self." In the novel Dead Souls, the landowner Korobochka laments that her serf-blacksmith burned up: "Something inside him started burning somehow, he'd had too much to drink. A blue flame just came out of him, and he smoldered and smoldered all over, and turned black as charcoal, and he was such a really skillful blacksmith!."
Jules Verne describes in his novel Dick Sand, A Captain at Fifteen (1878) that when a fictional African "King of Kazounde" tasted a punch set aflame, "An act of spontaneous combustion had just taken place. The king had taken fire like a petroleum bonbon. This fire developed little heat, but it devoured nonetheless." Verne has no doubt about SHC being the result of alcoholism : "In bodies so thoroughly alcoholized, combustion only produces a light and bluish flame, that water cannot extinguish. Even stifled outside, it would still continue to burn inwardly. When liquor has penetrated all the tissues, there exists no means of arresting the combustion."
In the video game Twisted Metal III, the character Damien Cole is described as having "mastered the fine art of spontaneous combustion", leading others to believe he has lighter fluid coursing through his veins.
In the novel Brimstone (book) (2004) by Douglas Preston and Lincoln Child spontaneous human combustion is discussed as a possible cause of death in some homicides.
In the movie Repo Man, the incineration of a police officer by the mysterious object in the trunk of a car is cited as an example of spontaneous human combustion by a government agent ("It happens sometimes. People just explode.")
In the episode "Soft Light" of the television series The X-Files some murder victims are thought to have died via spontaneous human combustion.
In the animated television series South Park, the episode "Spontaneous Combustion" involves many people in the town suddenly bursting into flames. Stan Marsh's father finds out this is caused by intestinal gas.
In the film This Is Spinal Tap several of the band's drummers died of freak accidents, including one who spontaneously combusted on stage, leaving behind only a "globule". David St. Hubbins stated "Dozens of people spontaneously combust every year; it's just not very widely reported."
In the BBC TV series New Tricks, an episode called Big Topped featured an apparently impossible crime involving incineration inside a locked circus caravan; spontaneous human combustion is suggested as an explanation, although this is later rejected. At one point one of the characters replicates the QED experiment referred to above.
There's one mystery I'm asked about more than any other: spontaneous human combustion. Some cases seem to defy explanation, and leave me with a creepy and very unscientific feeling. If there's anything more to SHC, I simply don't want to know.|20px|20px|Arthur C. Clarke (1994)
The opinion that a man can burn of himself is not founded on a knowledge of the circumstances of the death, but on the reverse of knowledge - on complete ignorance of all the causes or conditions which preceded the accident and caused it.|20px|20px|Justus von Liebig (1855)